gentamicin (Rx)

Brand and Other Names:
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

injectable solution

  • 10mg/mL
  • 40mg/mL

Intravenous solution

  • 60mg (50mL)
  • 70mg (50mL)
  • 80mg (50mL, 100mL)
  • 90mg (100mL)
  • 100mg (50mL, 100mL)
  • 120mg (100mL)
more...

In underweight and nonobese patients, use of total body weight (TBW) instead of ideal body weight for determining initial mg/kg/dose is accepted; ideal body weight (IBW) also may be used to determine doses for patients who are neither underweight nor obese

Susceptible Infections

Conventional dosing

  • 3-5 mg/kg/day IV/IM divided q8hr  

Extended dosing interval

  • Initial: 5-7 mg/kg/dose IV qDay 
  • Not for use in patients with ascites, burns covering >20% of total body surface area, cystic fibrosis, end-stage renal disease, endocarditis, infants, mycobacterial infections, or pregnancy
  • Measure gentamicin level between 6 and 14 hr after initiating gentamicin infusion; use institution-specific nomogram to determine appropriate dosing interval

Surgical Prophylaxis (Off-label)

5 mg/kg IV as single dose 1 hr prior to surgical incision; alternativley, 1.5 mg/kg IV as single dose for gynecology procedures 

Dose is based on actual body weight (TBW) unless body weight is >20% above ideal body weight (IBW), in which case the dosing weight can be estimated by IBW + 0.4 (TBW - IBW)

Infective Endocarditis Treatment

Enterococcus (native or prosthetic valve); Off-label dose

  • 3 mg/kg/day IV/IM divided q8hr for 4-6 weeks in combination with a beta-lactam and for 6 weeks when administered wiht vancomycin 
  • Organism sensitivity testing should determine choice of concomitant antiibotic and treatment duration

S. aureus (prosthetic valve; methicillin susceptible or resistant); Off-label dose

  • 3 mg/kg/day IV/IM divided q8-12hr for 3-5 days for native valve infections or for 2 weeks for prosthetic valve infections in combination with other antibiotic 
  • Organism sensitivity testing should determine choice of concomitant antibiotic

Viridans group streptococcus and S. bovis (native or prosthetic valve); Off-label use

  • 3 mg/kg/day IV/IM qDay (preferred) or divided q8hr for 2 weeks for native or prosthetic valve infections or for 6 weeks for prosthetic valve infections with relatively or fully resistant strains in combination with other antibiotic 
  • Organism sensitivity testing and source of infection should determine choice of concomitant antibiotic

Cystic Fibrosis (Off-label)

7.5-10.5 mg/kg/day IV/IM divided q8hr  

Pelvic Inflammatory Disease (Off-label)

Loading dose: 2 mg/kg IV or IM  

Maintenance dose: 1.5 mg/kg IV/IM q8hr plus clindamycin IV or 3-5 mg/kg IV qDay

May initiate transition from parenteral to oral therapy of either oral doxycycline or oral clindamycin within 24-48 hr of clinical improvement for total treatment duration of 14 days

Plague (Yersinia pestis) Treatment; Off-label use

5 mg/kg IV/IM qDay for 10 days or 2 mg/kg IV/IM loading dose; then 1.7 mg/kg/dose IV/IM q8hr for 10-14 days or until 2 days after patient is afebrile; doxycycline, ciprofloxacin, or chloramphenicol could be used as third-line alternatives 

Mycobacterium Infection (Orphan)

Gentamicin liposome injection: For disseminated Mycobacterium avium-intracellulare infection

Orphan indication sponsor

  • Liposome Company, Inc; One Research Way; Princeton, NJ 08540

Dosing Considerations

Gentamicin may be administered IV/IM

Infuse over 30-120 min when administering IV

Dosing regimens are numerous and are adjusted based on CrCl and changes in volume of distribution, as well as on the body space where distribution of the agent will occur

Monitor peak (4-12 mg/L) and trough (1-2 mg/L)

Monitor nephrotoxicity, neurotoxicity, and ototoxicity; assess at beginning of therapy and throughout

Each regimen must be followed by at least trough level drawn on third or fourth dose, 30 min before dosing unless renal toxicity suspected

May draw peak level 30 min after 30-min infusion has been completed or 1 hr after IM injection

Use ideal body weight for mg/kg/dose; more accurate than total body weight

Gentamicin is usually a first-line aminoglycoside against infections with gram-negative organisms such as Pseudomonas aeruginosa, Proteus, Escherichia coli, Klebsiella, Enterobacter, Serratia, and Citrobacter, as well as against Staphylococcus (gram- positive)

Bacterial organisms causing susceptible infections

  • Susceptible infections include the following:
  • Pseudomonas aeruginosa
  • Proteus species (indole-positive and indole-negative)
  • Escherichia coli
  • Klebsiella-Enterobacter-Serratia species
  • Citrobacter species
  • Staphylococcus species (coagulase-positive and coagulase-negative)
  • Pseudomonas aeruginosa
  • Proteus species (indole-positive and indole-negative)
  • Escherichia coli
  • Klebsiella-Enterobacter-Serratia species
  • Citrobacter species
  • Staphylococcus species (coagulase-positive and coagulase-negative)

Dosing Modifications

Renal impairment

Conventional dosing

  • Renally adjusted dose recomendations are based on doses of 1.7 mg/kg/dose q8hr or 5-7 mg/kg/dose once daily 
  • CrCl>50 mL/min: No dosage adjustment necessary
  • CrCl 10-50 mL/min: Administer q12-48 hr
  • CrCl<10 mL/min: Administer q48-72 hr

Once daily (interval adjustment of extended interval dosing)

  • Adjust doses based on serum concentrations and organism MIC
  • CrCl≥60mL/min: No dosage adjustment necessary
  • CrCl 40-59 mL/min: 5-7 mg/kg IV q36hr 
  • CrCl 20-39 mL/min: 5-7 mg/kg IV q48hr
  • CrCl<20 mL/min: 5-7 mg/kg IV once; monitor serum levels and redose when gentamicin level is < 1 mcg/mL

Intermittent hemodialysis

  • Administer after hemodialysis on dialysis days
  • Dependent on patients size, site of injection, filter, duration and type of intermittent hemodialysis, it is ~30-50% dialyzable
  • 1-1.7 mg/kg IV/IM after initial hemodialysis session; serum gentamicin concentrations should guide subsequent dosing 
  • Dosing dependent on assumption of 3 times/wk complete intermittent hemodialysis sessions

Peritoneal dialysis

  • Intermittent dosing: 0.6 mg/kg per exchange once daily for anuric patients; 0.75 mg/kg/dose IP for non-anuric patients qDay during long dwell periods; depending on infecting organism and patient's clinical status, may treat for 2-3 weeks 
  • Continuous dosing: 8 mg/L loading dose; followed by 4 mg/L maintenance dose

Continuous renal replacement therapy

  • Drug clearance is highly dependent on method of renal replacement, filter type, and flow rate; close monitoring of pharmacologic response, sign of adverse reactions due to accumulation, and target drug concentration necessary for appropriate dosing
  • 3 mg/kg/day IV/IM divided q8hr; may administer up to 5 mg/kg/day IV/IM divided q6-8hr in life-threatening infections; peak; adjust dose based on serum concentration monitoring; peak concentration >12 mcg/mL should be avoided 

Dosage Forms & Strengths

injectable solution

  • 10mg/mL
  • 40mg/mL

Intravenous solution

  • Intravenous solution
  • 60mg (50mL)
  • 70mg (50mL)
  • 80mg (50mL, 100mL)
  • 90mg (100mL)
  • 100mg (50mL, 100mL)
  • 120mg (100mL)
more...

Use of ideal body weight (IBW) for determining the mg/kg/dose appears to be more accurate than on the basis of total body weight (TBW)

Susceptible Infections

Infants: 2.5 mg/kg/dose IV/IM q8hr

Children and adolescents:: 2-2.5 mg/kg/dose IV/IM q8hr 

<30 weeks' gestation

  • 0-28 days: 2.5 mg/kg/day IV/IM 
  • >28 days: 3 mg/kg/day IV/IM

30-36 weeks' gestation

  • 0-14 days: 3 mg/kg/day IV/IM  
  • >14 days: 5 mg/kg/day IV/IM divided q12hr

>36 weeks' gestation

  • 0-7 days: 5 mg/kg/day IV/IM divided q12hr  
  • >7 days: 7.5 mg/kg/day IV/IM divided q8hr

Surgical Prophylaxis, Preoperative (Off-label use)

2.5 mg/kg IV/IM within 60 min piror to surgical incision or without antibiotics; procedure dependent 

Dose is based on actual body weight unless >20% above ideal body weight; then dosage requirement may best be estimated using a dosing weight of IBW + 0.4 (TBW- IBW)

Dosing Considerations

Monitor peak (4-12 mg/L) and trough (1-2 mg/L)

Monitor nephrotoxicity, neurotoxicity, and ototoxicity; assess at beginning of therapy and throughout

Individualization critical due to low therapeutic index

Use ideal body weight for mg/kg/dose, except in neonates (in whom actual body weight should be used)

Bacterial organisms causing susceptible infections

  • Pseudomonas aeruginosa
  • Proteus species (indole-positive and indole-negative)
  • Escherichia coli
  • Klebsiella-Enterobacter-Serratia species
  • Citrobacter species
  • Staphylococcus species (coagulase-positive and coagulase-negative)

Dosing Modifications

GFR>50 mL/min/1.73m²: No dosage adjustment necessary

GFR 30-50 mL/min/1.73m²: Administer q12-18hr

GFR 10-29 mL/min/1.73m²: Administer q18-24hr

GFR <10 mL/min/1.73m² Administer q48-72hr

Intermitent hemodialysis: 2 mg/kg/dose; redose as indicated by serum concentration

Peritoneal dialysis: 2 mg/kg/dose; redose as indicated by serum concentration

Continuous renal replacement therapy: 2-2.5 mg/kg/dose q12-24hr; monitor serum concentration 

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Interactions

Interaction Checker

and gentamicin

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    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            >10%

            Neurotoxicity (vertigo, ataxia)

            Gait instability

            Ototoxicity (auditory, vestibular)

            Nephrotoxicity (decreased CrCl)

            Nephrotoxicity if trough >2 mg/L

            1-10%

            Edema

            Rash

            Reddening of skin

            Itching

            <1%

            Drowsiness

            Headache

            Pseudomotor cerebri

            Photosensitivity

            Allergic reaction

            Erythema

            Anorexia

            Nausea/vomiting

            Weight loss

            Increased salivation

            Enterocolitis

            Granulocytopenia

            Agranulocytosis

            Thrombocytopenia

            Elevated LFTs

            Burning

            Stinging

            Tremors

            Muscle cramps

            Weakness

            Dyspnea

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            Warnings

            Black Box Warnings

            Patients treated with aminoglycosides should be under close clinical observation due to potential toxicity associated with their use

            Neurotoxicity, manifested as bilateral auditory and vestibular ototoxicity, can occur in patients with preexisting renal impairment and in patients with normal renal function treated at higher doses and/or for periods longer than those recommended; high-frequency deafness usually occurs first and can be detected only with audiometric testing

            Aminoglycosides are potentially nephrotoxic; risk is greater in patients with impaired renal function and in those who receive high doses or prolonged therapy; rarely, nephrotoxicity may not become apparent until the first few days after cessation of therapy

            Use with caution in premature infants and neonates because of renal immaturity and the resulting prolongation of serum half-life of the drug

            Monitor eighth cranial nerve and renal function; especially in patients with known or suspected reduced renal function at onset of therapy and also in patients with normal function at the beginning of therpay but that develop signs of rena dysfunction during therapy; examine urine for increased excretion of protein, decreased specific gravity and presence of cells; serial audiograms should be obtained when  possible; adjust the dose or discontinue therapy if there is evidence of ototoxicity or nephrtoxicity

            Neuromuscular blockade and respiratory paralysis have been reported following parenteral injection, topical instillation (as in orthopedic and abdominal irrigation or in local treatment of empyema), and oral use of aminoglycosides, especially when given soon after anesthesia or muscle relaxants; if blockage occurs, calcium salts may reverse these phenomena, but mechanical respiratory assistance may be necessary

            Avoid concurrent or sequential use of neurotoxic and/or nephrotoxic drugs, including other aminoglycosides (eg, amikacin, streptomycin, neomycin, kanamycin, paromomycin)

            Cumulative listing of drugs to avoid from all aminoglycosides; package inserts includes amphotericin B, bacitracin, cephaloridine, cisplatin, colistin, polymyxin B, vancomycin, and viomycin

            Avoid potent diuretics (eg, ethacrynic acid, furosemide) because they increase risk of ototoxicity; when administered intravenously, diuretics may enhance aminoglycoside toxicity by altering antibiotic concentrations in serum and tissue

            Contraindications

            Prior aminoglycoside toxicity or hypersensitivity

            Cautions

            Patients treated withaminoglycosides should be under close clinical observation; high risk of toxicity associated with their use

            Risk of ototoxicity; tinnitus or vertigo may be indications of vestibular injury and impending bilateral irreversible damage; discontinue therapy if signs of ototoxicity occur

            Risk of nephrotoxicity; other factors that increase patient risk of ototoxicity include advanced age and dehydration

            Narrow therapeutic index (not intended for long-term therapy)

            Caution in renal failure (not on dialysis), myasthenia gravis, hypocalcemia, and conditions that depress neuromuscular transmission

            Adjust dose in renal impairment

            Endocarditis prophylaxis (GI, GU procedure): AHA Guidelines recommend only for high-risk patients

            Diuretics may enhance aminoglycoside toxicity by altering antibiotic concentration in serum and tissue; certain diuretics by themselves may cause ototoxicity; avoid potent diuretics, including ethacrynic acid or furosemide

            Use caution in patients with electrolyte abnormalitie including hypocalcemia, hypomagnesemia, or hypokelemia

            Use caution in patients with neuromuscular disorders, including myasthenia gravis

            Use caution in patients with hearing and renal impairment

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            Pregnancy & Lactation

            Pregnancy category: D

            Lactation: Enters breast milk; use with caution (AAP Committee states "compatible with nursing")

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

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            Pharmacology

            Mechanism of Action

            Aminoglycoside antibiotic for coverage of gram-negative bacteria, including Pseudomonas species; synergistic with beta lactamase against enterococci; interferes with bacterial protein synthesis by binding to 30S and 50S ribosomal subunits

            Absorption

            Peak plasma time: IM (30-90 min); IV (30 min after 30-min infusion)

            Distribution

            Gentamicin crosses placenta; relative diffusion from blood into CSF is minimal even with inflammation

            CSF-to-blood level ratio: Normal meninges (minimal); inflamed meninges (10-30%)

            Protein bound: <30%

            Vd: Neonates (0.4-0.6 L/kg); children: (0.3-0.35 L/kg); adults: (0.2-0.3 L/kg); Vd increased by edema, ascites, and fluid overload and decreased by dehydration

            Elimination

            Half-life: 2-3 hr (NRF)

            Renal clearance: Directly related to renal function

            Excretion: Urine (70% recovered as unchanged drug in patients with NRF)

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            Administration

            IV Incompatibilities

            Additive: Ampho B, ampicillin, cefazolin, dopamine, furosemide, heparin

            Syringe: Ampicillin, heparin

            Y-site: Furosemide, heparin

            Not spec: Carbenicillin

            IV Compatibilities

            Additive: cimetidine, clindamycin, verapamil

            Syringe: clindamycin

            Y-site: Amiodarone, esmolol, vitamins B/C

            IV Preparation

            Dilute single dose in 50-200 mL NS or D5W

            IV Administration

            Infuse over 30 min-2 hr

            After infusion, flush line with NS or D5W

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            Formulary

            FormularyPatient Discounts

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            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
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            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
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            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
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            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.